Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Physical dimension specified
Patent
1991-11-12
1993-04-20
Schofer, Joseph L.
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Physical dimension specified
526245, 526263, 526298, 526304, 526309, 526311, 4284111, 428 64, 4274343, B32B 2730
Patent
active
052041786
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to novel (meth)acrylate copolymers which have nonlinear optical properties and which can form solid monomolecular Langmuir-Blodgett films.
The present invention furthermore relates to the use of the novel (meth)acrylate copolymers in nonlinear optics and Langmuir-Blodgett films which are obtained using the novel (meth)acrylate copolymers.
The present invention also relates to a novel process for the uniform spatial orientation of organic radicals.
Nonlinear optics is concerned very generally with the interaction of electromagnetic fields in different substances and the associated field-dependent refractive index in these substances.
Very generally, a substance emits light if dipoles oscillate in it, the frequency of the emitted light wave being equal to the oscillation frequency of the dipoles. If the oscillating dipoles contain a plurality of frequency components, all of these occur in the light emitted by the relevant substance. If the dimensions of the substance are greater than the wavelength of the emitted light, the identical dipoles oscillating in the substance should as far as possible oscillate in the same direction and with a phase difference which ensures that the light emitted by a volume element is not extinguished by destructive interference with the light emitted by another volume element.
In a polarizable substance, macroscopic polarization P, which is defined as the dipole moment per unit volume, is induced by an external electric field
If the polarizable substance does not contain any permanent molecular dipoles, the dipole moment and hence the macroscopic polarization from a shift of the electrons by an amount d away from their rest position, i.e. from the center of the positive charge. On the other hand, if the polarizable substance contains permanent dipoles, the applied electric field E results in a change in the permanent dipole moment by the same mechanism.
As long as the shift d remains proportional to the electric field E, the polarization P is also proportional to the electric field E, which is expressed by the known linear equation 1 .chi. is the dielectric susceptibility.
If the external electric field is increased, every substance must of course exhibit a deviation from the linear law according to Equation 1 above a field strength specific to it. The mechanical analog to this is the deviation from Hook's law when a spring is overloaded. Such deviations from linearity are most simply handled mathematically by adding a parabolic term and higher powers of the variables, i.e. the nonlinear function is expanded by powers of the variable resulting in Equation 2 EE+.chi..sup.(3) EEE . . . ) Equation 2 finally responsible for linear optical behavior of the relevant substance, second order nonlinear optical behavior in the relevant substance, and responsible for the third order nonlinear optical behavior of the relevant substance.
Both .chi..sup.(2) and .chi..sup.(3) are material constants which are dependent on the molecular structure, the crystal structure, the frequency of light and in general also the temperature. It is known that they can be determined by the dynamic holographic method of "four wave mixing", as described by
W. W. Schkunow et al. in Spektrum der Wissenschaft, February 1986, pages 92 to 97, and
J. P. Huignard et al. in SPIE Volume 215, Recent Advances in Holography, pages 178 to 182, 1980.
Substances having a dielectric susceptibility .chi..sup.(2) dependent on the field strength, i.e. having nonlinear second order optical properties, give rise to a number of dispersive processes, such as frequency doubling (second harmonic generation, SHG), which permits the production of light having half the wavelength of the incident light, the electrooptical effect (Pockels' effect), which permits a change in the refractive index when an electric field is applied, or sum and difference frequency mixing, and frequency mixing which permits the continuous adjustment of laser light, resulting in many technical applications. Examples are the electroopti
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Hawley's Condensed Chemical Dictionary, 11th Ed., Van Nostrad, New York, 1987, p. 35.
Optische Phasenkonjugation; Schkunow et al., Spektrum der Wissenschaft, Feb. 1986, 92-97 (German).
Dynamic holography and coherent four wave . . . , Hulgnard et al., SPIE vol. 215 Recent Advances in Holography (1980).
Nonlinear Optical Polymer Systems and Devices, Ulrich, Mol. Cryst. Liq. Cryst., 1988, vol. 160, pp. 1-31.
Some New Side-Chain Liquid Crystalline . . . , Barny et al., SPIE vol. 682 Mol. and Poly. Optoelectronic Materials; Fundamentals and Applications, 1986.
The Characterization of Langmuir-Blodgett . . . , Carpenter et al., Thin Solid Films, 161 1988, 315-324.
Fuchs Harald
Funhoff Dirk
Licht Ulrike
Schrepp Wolfgang
Schupp Hans
BASF - Aktiengesellschaft
Nagumo M.
Schofer Joseph L.
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